Jerry (the OP),
Your post kindof hinted at two competing goals.
The best RV battery and not wanting to spend a fortune on a battery of course don't usually come together in the same product.
Here's, in my opinion, the best RV battery available:
http://www.lithiumion-batteries.com/index.phpHere's, in my opinion, the best AGM RV battery available:
http://rollsbattery.com/public/specsheets/12FS125.pdf